Network configurations wherein power and communication signals are delivered to network devices using the same bus are known in the art. One such network configuration uses what is known as Digital Addressable Lighting Interface (DALI), which defines a network interface standard used for controlling lighting network devices. DALI is an example of a two-wire configuration, wherein a two-wire bus is coupled between the network devices to deliver power to the devices and to support communication between the devices. Communication is established on the bus in a DALI network by indicating a logical “1” with the presence of voltage between the two wires and a logical “0” by shorting of the two wires by any device.
In general, the devices in a network using the same bus for power supply and communication are only supplied with power at certain times during communication, e.g. between communication signals and/or during the time period of any logical “1” of a communication signal. A device with no auxiliary power, i.e. a device powered entirely by power delivered on the network bus, may therefore be configured to store energy to support operation of the device during times where no power can be obtained from the bus, and the device may replenish the stored energy at other times.
The current available from the bus in these configuration determines how long it takes to replenish stored energy in the network devices, but large in-rush currents during energy storage periods can distort the communication signals, e.g. the logical “1”s. To address this some systems add a current limit circuit to the network power supply. Adding a current limit to the power supply reduces the impact on the communication signals, but increases the time required to replenish the energy stored in the devices.